There has been known a connector, which connects a fuel feeding pipe or an air pipe to a fuel tank having at least an outer layer formed of a synthetic resin, and which includes a base member having a flange and a passage, an outer melt-bonding projection and an inner melt-bonding member, the flange being of such a size as to cover an opening formed to pass through the fuel tank, the passage communicating with the fuel feeding pipe or the like, the outer melt-bonding projection disposed on a projecting end of the flange of the base member, and the inner melt-bonding member being formed in a ring shape (see Patent Document 1 identified below).
In the connector disclosed in Patent Document 1, it is possible to unify the outer melt-bonding projection and the inner melt-bonding member since the outer melt-bonding projection and the inner melt-bonding member are adapted to each other because of being formed of polyethylene or an alloy containing polyethylene. On the other hand, in this connector, the base member, which is formed of a synthetic resin having a gas barrier property (a synthetic resin difficult to pass a gas, such as hydrocarbon, produced from fuel therethrough; e.g. a polyacetal resin disclosed as one example in Patent Document 1), is not adaptable with the synthetic resin forming the inner melt-bonding member. For this reason, it has been impossible to unify a lower surface of the flange of the base member and an upper side of the inner melt-bonding member even by molding the inner melt-bonding member by insert-molding with the base member used as an insert, or by simultaneously molding both of the flange and the inner melt-bonding member. In such a circumstance, since a gas, which has arrived at the lower surface of the flange through the opening of the fuel tank, reaches an inner lateral side of the outer melt-bonding projection through an contact interface between the lower surface of the flange and the upper side of the inner melt-bonding member, there has been no other way but to reduce the leakage of the gas by increasing the wall thickness of the outer melt-bonding projection.
Patent Document 1: JP-A-2002-211254